Air-o-space heater means for recovering heat from a fluid steam

ABSTRACT

The present invention constitutes a means for effectuating the partial recovery of heat normally lost through a flue pipe or exhaust stack of a domestic or industrial heating system. Use is made of a plurality of heat pipes secured in a fixed mutual relationship. Said plurality is partially extended into the flue pipe. Heat is axially transferred from the flue pipe and into an air duct that is equipped with a fan. The fan creates convection currents which serve to advance the recovered heat within the heat duct and ultimately back to either the industrial plant or residence wherein the recovered heat may be utilized for whatever heating purpose is desired.

United States Patent 1 1 1111 3,884,292

Pessolano et al. 1 1 May 20, 1975 15 1 AIR-O-SPACE HEATER MEANS FOR3,779,310 12/1973 Russell 165/105 RECOVERING HEAT FROM A FLU) 3,788,388l/l974 Barkmann 165/105 X STEAM FOREIGN PATENTS OR APPLICATIONS V [75]inventors: Richard L. Pessolano. Sparta; Robin 554,345 6/1943 UnitedKingdom 165/105 B. Rhodes, Parsippany, both of NJ. 73 Assignee;[Sahel-mics Inc" Augusta NJ Primary liraminer-Albert W. Davis, Jr.

Attorney, Agem, or Firm-Mel K. Silverman, Esq.

' [22] Filed: June 22, 1973 1211 Appl. No.: 372,525 57 ABSTRACT Thepresent invention constitutes a means for effecl l tuating the partialrecovery of heat normally lost 6/l0l through a flue pipe or exhauststack of a domestic or [51] int. Cl. F28d 15/00 industrial heatingsystem. Use is made of a plurality of Field of Search heat pipes securedin a fixed mutual relationship. Said 237/8, 17; 219/370; 236/1 1, 49;126/10] plurality-is partially extended into the flue pipe. Heat isaxially transferred from the flue pipe and into an air [56] ReferencesCited duct that is equipped with a fan. The fan creates con- UNITEDSTATES PATENTS vection currents which serve to advance the recovered 1546 450 7 1925 Meaker 165/179 x heat within the heat duct W ultimately Pto either 1 3, 8/1929 the industrial plant or res1dence wherem therecov- 2,092,658 9/1937 ered'heat may be utilized for whatever heatingpur- 2,362,940 1 1/1944 pose is desired.

2,529,915 ll/l950 1 Claim, 3 Drawing Figures In I jllll l AIR-O-SPACEHEATER MEANS FOR RECOVERING HEAT FROM A FLUID STEAM BACKGROUND OF THEINVENTION what might be termed a method of heat recycling or of energyconservation.

The theoretical basis of the present invention rests upon developmentsin an area of heat exchange technology which relate to isothermaldevices. One isothermal device which has received considerable note inrecent years is a device which is popularly known as a heat pipe. A heatpipe is, in its simplest form, a closed container, normally metallic,employing on its inner surface a capillary wick structure which isessentially saturated with the liquid phase of a working field. Thecapillary structure may be comprised of grooves, of single or multiplelayers of wire screen, or of any other suitable system of capillariescapable of moving the liquid-phase working fluid from a condenser orheat sink end of the heat pipe to an evaporator or heat source end.

The container is also filled with the vapor of the working fluid, andthe container is sealed under a partial vacuum such that the vapor andliquid phases of the working fluid are in equilibrium. The heat pipetransfers heat from one area on the external surface of the container toanother area by a vaporizationcondensation cycle.

In addition, the heat pipe is a totally closed, mechanically staticdevice capable of axially transporting large quantities of heat in anessentially isothermic fashion. In addition it is not dependent upongravity for its operation.

The present invention presents, as will be shown below, a novel use ofthe heat pipe in order to effect the recovery of heat from a fluid steamand, more particularly, from exhaust gases in residential and industrialheating systems.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a means for the recovery of heat from waste gases produced byresidential and industrial heating processes.

Another object is to provide a means of conservation of thermal energy.

A yet further object is to provide a means of increasing the efficiencyof an otherwise conventional heating system.

A further object is to provide a heat recovery means intended to reducethe cost of operationn of conventional heating systems.

The above objects are obtained'by the insertion of a plurality of heatpipes, disposed in fixed mutual relationship, into the heat exhaustchannel of a heating system such as a furnace. Said plurality of heatpipes,

while in no way interfering with the exhaust function of the duct intowhich they are inserted, will effect the axial transfer of thermalenergy through said heat pipes toward those ends of said heat pipes thatare opposite to the ends inserted into said exhaust duct. Said oppositeends of said heat pipes, which receive the recovered heat, are enclosedby a second duct, separated by a solid fluid-tight wall from saidexhaust duct.

Enclosed within said second duct is a fan. A source of cool air isreceived at the intake of said fan and advanced into said second duct,across the condenser ends of said heat pipes. The initially cool air isthereby heated by the thermal energy released at said condenser ends ofthe heat pipes. This heated air is then convected away from the heatpipes and fed back into the residential or industrial building for anyuse that may be desired.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of oneembodiment of the present invention.

FIG. 2 is a perspective schematic view of the present invention insertedinto the flue gas exhaust stack of a furnace.

FIG. 3 is a cross-sectional schematic view of the present invention.

DETAILED DESCRIPTION OF THE INVENTION A generalized schematic view ofthe concept utilized in the present invention is illustrated in FIG. 3.At the top of said figure is illustrated a hot flue gas ex haust duct10. The duct 10 can be taken as representative of any hot gas exhaustduct coming from such systems as a furnace, an incinerator, a fossilfuel combustion system, a chemical sytem utilizing an exothermicreaction, or any other heat generating apparatus or system. In otherwords, the duct 10 is to be considered as a generalized hot fluid streamthat, in a given instance, one may find exhausting from a residential orindustrial structure.

One or more heat pipes 12, which may be mutually secured in what istermed a fin-plate configuration, are extended into the duct 10. Theextended portions of the heat pipes 10 will, in most configurations,occupy less than 20 percent of the cross-sectional area of the duct 10.It is to be noted that flue gas temperatures in an oil-fired system canrange from 400 F. to 900 F., depending upon the system efficiency aswell as upon other factors.

Each heat pipe 10 absorbs a portion of this flue gas heat and transmitsit through the solid wall 14 and outside of the exhaust duct 10. Thewall 14 prevents any of the gases from escaping from the exhaust duct.

It is to be noted that the transfer of heat from the duct 10 to a secondduct 16 occurs in an isothermal fashion. This is to say, because of theisothermal properties of heat pipes, the temperature gradientsthroughout the system are minimized. The engineering value of such anisothermal heat transfe rvis that thermal stresses within the elementsof the present mechanism are reduced to a level not heretoforeobtainable in heat transfer technology. Thermal stress, which is causedby large temperature gradients and by differing coefficients ofexpansion in adjoining materials, generally contributes to a decrease inthe structural integrity, and therefore in the effective working life,of many heat transfer devices.

A fan 18 draws in cool air from the surrounding environment (see FIG. 3)and forces it over the length of the finned heat pipe portion 20. Thisprocedure serves to heat the air within the duct 16, which can then bechannelled for use in other areas of a house or plant. For example, in aresidential application, the hot air duct 16 can easily be fed into thebasement area of a house in order to provide additional warmth theretoand also to decrease the total heat load upon the furnace.

A unit of the above described class, when utilized in a flue pipe of aconventional residential furnace, can produce a recovered heat output ofbetween 5,000 and 10,000 BTUs. Such a unit may be provided with athermostat 22 which serves to control the fan 18. All of said componentsare UL-approved and may be easily installed into a 6-inch T-duct.

The unit can be used on steam, hot water and warm air systems and thuswill operate with any heating system.

A notable feature of the present invention is the ease with which it canbe installed, requiring little if any modification of the existingheating system. Once installed, the duct 16 can carry recycled heat toany given area. It will not only dry out dampness and eliminate odors inthe basement but will also keep the first level floors more confortablethan they would otherwise be.

Another utility of the present heat-recovery system lies in its use withwarm air heating systems. In such systems, the recycled heat can beducted into the return air intake of the furnace, thereby serving topreheat the air and thus increasing the total system efficiency bybringing more heat (if desired) to all parts of the home.

It is to be emphasized that the air coming out of the present heatrecovery means 16 is as pure as the air going into the intake side atthe fan 18. The design of the present device renders it impossible forcontaminated air to be carried with the heat from the stack 10. Saidmetal barrier 14 seals the stack gases on one side while keeping thenewly heated air on the other. Hence, there can be no air flow betweenthe two ducts and 16.

It is to be noted that the first (in duct 10) and second (in duct 16)portions 12 and respectively of the heat pipes may be adjusted in theirmutual relative lengths. This is achieved by providing the opening inthe wall 14, through which the pipes pass, with an interior threadingwhich is complementary to the exterior threading, or fin structure, ofsaid pipes. Through the rotation of said pipes their axial location canbe changed, thus altering the lengths of said first and second portions.Any increase in the length of the first portion 12 will increase thequantity of heat transferred from the duct 10; any decrease in lengthwill reduce the quantity of heat transferred.

Also it is. to be noted that the cool air intake at fin 18 may beequipped with a volumetric flow control.

A particularly compelling aspect of the present heat recovery means isits economics: the only expense entailed in the operation of said meansderives from the small amount of electricity which is needed to powerthe fan 18. Not only is no additional fuel required but, as aforestated,heat normally wasted is extracted by the heat pipes and returned intothe basic system.

In a normal residential unti, the present heat recovery means canincrease the efficiency of the heating system by approximately 10percent. This figure is derived from conventional combustion efficiencymeasurements. It is believed that the expense saved in fuel alone woulddefray the retail cost of the present heat recovery means within a fewmonths of installation. After such time the additional recovered heatwould represent a complete and total savings to the user.

While there is hereby shown and described the preferred embodiments ofthe present invention, it will be understood that the invention may beembodied otherwise than as herein specifically illustrated or described,and that in the illustrated embodiments certain changes in the detailsof construction and in the form and arrangement of the parts may be madewithout departing from the underlying idea or principles of thisinvention within the scope of the appended claims.

Having thus described our invention, what we claim as new, useful andnonobvious, and accordingly secured by Letters Patent of the UnitedStates is:

v l. A means for recovering heat from a first fluid stream, said fluidstream having a defined heat content, comprising:

a. a heat pipe having a first portion and a second portion, said firstportion extending into said fluid stream;

.b. a wall proximately disposed to said stream, said wall adapted toconfine said stream in order to prevent heat and fluid leakage from saidstream, said wall defining the division between said first and secondportions of said pipe;

0. means for proving a second fluid stream, said second stream having adifferent temperature than said first stream, said second streamdisposed in thermal contact with said second portion of said heat pipe,wherein heat transfer is effectuated from the fluid stream of highertemperature to the fluid stream of lower temperature;

d. exteriorly accessible means for mutually adjusting the relativelengths of said first and second portions of said heat pipe, wherein thetotal length of said heat pipe remains constant,

whereby the adjustment of the length of said first portion effectuates aregulation of the quantity of heat transferred between said first andsecond fluid streams; and

e. a blower control for said second flow stream said blower controlserving to maintaining a desired rate of flow of said second flow streamwith respect to said second portion of said heat pipe.

1. A means for recovering heat from a first fluid stream, said fluidstream having a defined heat content, comprising: a. a heat pipe havinga first portion and a second portion, said first portion extending intosaid fluid stream; b. a wall proximately disposed to said stream, saidwall adapted to confine said stream in order to prevent heat and fluidleakage from said stream, said wall defining the division between saidfirst and second portions of said pipe; c. means for proving a secondfluid stream, said second stream having a different temperature thansaid first stream, said second stream disposed in thermal contact withsaid second portion of said heat pipe, wherein heat transfer iseffectuated from the fluid stream of higher temperature to the fluidstream of lower temperature; d. exteriorly accessible means for mutuallyadjusting the relative lengths of said first and second portions of saidheat pipe, wherein the total length of said heat pipe remains constant,whereby the adjustment of the length of said first portion effectuates aregulation of the quantity of heat transferred between said first andsecond fluid streams; and e. a blower control for said second flowstream said blower control serving to maintaining a desired rate of flowof said second flow stream with respect to said second portion of saidheat pipe.